Propellant and process for manufacturing



l atented Apr. 27, 1948 'PROPELLANT AND PROCESS FOR MANUFACTURING 1George C. Hale, Dover, N. .L, assignor to the United States of Americaas represented by the Secretary of War No Drawing. Application March 20,1939, Serial No. 263,047

(Granted under the act of March 3, 1883, as

16 Claims.

amended April 30, 1928; 370 0. G. 757) The invention described herein mabe manufactured'and used by or for the Government for governmentalpurposes, without the payment to me of any royalty thereon.

This invention relates to a propellant and to a process of manufacturingthe same.

In the development of propellent powders for use in high velocity smallarms ammunition, it has been found necessary to employ compositions ofhigh potential or energy content and to coat such powders with some slowburning material to retard the rate of burning of the powder in theinitial stages of its combustion. Double base powders or powderscontaining nitroglycerin are commonly used to provide the high potentialrequired but up to the present time the attempts to coat such powders toobtain the highest possible velocities within practicable pressurelimits have not been altogether successful. The difiiculty has existedthat when nitroglycerin powders are provided with a coating to give thedesired velocities and pressures, a marked increase in the rate ofburning of the powders occurs after they are stored for a, brief time atslightly elevated temperatures, this resulting in extremely highpressures in a relatively short time after the ammunition is loaded.

The possible causes of this difiiculty are believed to be one or both ofthe following factors. The coating agent gradually dissolves in theliquid nitroglycerin contained in the powder and thus its efiect inretarding the rate of burning is eliminated; the higher the temperatureof storage the faster the solution occurs and the sooner the powderincreases in quickness of, burning; or if the coating applied to thepowder is relatively insoluble in nitrogylcerin the solution of thecoating can occur only to a limited extent but the tendency ofnitroglycerin to volatilize is always present and causes thenitroglycerin to gradually diffuse into the coating, thus increasing thespeed of burning of the coating so that the original effectiveness ofthe coating is lost.

, .With the above considerations as a basis, experiments have beenconducted in an effort to work out a method of preparing or formulatingcoated nitroglycerin powders which will not change in ballistics uponexposure to elevated temperatures such as may be encountered in storage.It has been found that if the nitroglycerin is first saturated with thematerial which is to be used as coating agent, the nitroglycerin powdercan then be coated with this particular agent and retain'itsefiectiveness even when subjected to a temperature of 120 F. for severalmonths; and

further the volatility of the nitroglycerin can be materially reducedeither by dissolving in it the material to be used as coating agent or ahigh potential explosive which functions ballistically similar tonitroglycerin. Obviously both procedures may be used in one and the samepowder. Specific examples of powders formulated in accordance with theabove procedures are as follows:

Per Nitrocellulose Nitroglycerin 20 Dinitrotoluene 1.2 Diphenylamine 1Per cent Nitrocellulose 71.2

Nitroglycerin 20 Dinitrotoluene 1.2 Trinitrotoluene 6.6

Diphenylamine 1 To each of these powders, after it was made of theproper grain dimensions, was added as a coating an amount ofdinitrotoluene, actually ,2 to 10%, suchas'is required to meet theballistic requirements of the particular weapon.

' It is, noted that in each of the above powders 1.2% dinitrotoluene wasused. This represents complete saturation of the nitroglycerin in thepowder-with dinitrotoluene as it was found by experiment that the latteris soluble in nitroglycerin to the extent of 6%. The second powderlisted contains 6.6% of trinitrotoluene which represents saturation ofthe nitroglycerin with trinitrotoluene, the solubility of the latter innitroglycerin having been found by experiment to be 33%. Powders made inaccordance with the method described were loaded in caliber .30ammunition and fired immediately after loading and then periodicallyduring storage at 50 C. (122 F.) over a period of seven months. Themeasured velocities and pressures at the end of the storage periodagreed closely with the values given by the ammunition before storage.In fact the differences were within the limits of experimental error,thus indicating that for all practical purposes the method offormulating the coated powders eliminated the difiiculty of change inrate of burning which has existed in the past when coated nitroglycerinpowders were used.

While it is known that dinitrotrotoluene has been used for years as acoating agent for nitrocellulose propellant powders, the method aboveoutlined of avoiding thechange inballistics that occurs when it is usedon nitroglycerin powders has not been previously disclosed, It is knownfurther that trinitrotoluene has been used extensively as an ingredientof nitroglycerin powders but the above method of using itinvolvingsatunation of the nitroglycerin and then applying a coatingagent which cannot dissolve'in-the nitroglycerin due to saturation of thnitroglycerin with the coating agent has not been previously disclosedso far as known. The :aboveprocedure effectively reduces the change inballistics of-coated nitroglycerin powders by preventing solution of thecoating agent in the nitroglycerin or diffusion of the nitroglycerininto the coating or both.

The above examples of the method of preparingnitroglycerin:nitroccllulose powders which are to .be coated withdinitrotoluene are .g-iven merely .to'demonstrate the principle which isinvolved in this invention. The general method is obviously applicableto -nitroglycerinenitrocellulose powders which are to be coated with anyagent vto retard the initial rate of burning of the powder. ,Forinstance dimethyldiphenylurea. has

been found to be soluble in nitroglycerin to the extent of 5.8%; if theformer is used as coating agent it is also added to the powdercomposition in an amount such as is sufiicient at least to saturate thenitroglycerin. Thus, for a powder containing 20% nitroglycerin, at least1.16% of dimethyl-diphenylurea should be added to the powder, while apowder containing 40% nitroglycerin would require at least 2.32% of theurea derivative; after these amounts of the latter compound are added tothe powder, any amount of the same compound desired may be used as acoating since none of the coating can dissolve in the saturatednitroglycerin. -On the other hand if a coating agent is used which isentirely insoluble in nitroglycerin, as for example, nitr-ogu'anidine,ethyleneclinitrami-ne, etc., it is necessary to add to the powdercomposition another compound which is sufliciently soluble innitroglycerin to reduce its volatility and thereby reduce the tendencyof the nitroglycerin to difiuse into and be absorbed by the coatingagent. While trinitrotoluene has been found'especially effective forthis, due to its high solubility in nitroglycerin; viz. 33%, tetryl witha solubility of 12% and other compounds soluble in nitroglycerin may be'used to fulfill the purpose, subject, of course, to the limitation thatthe compounds dissolved in the nitroglycerin shall not causeobjectionable 'decomposition of the nitroglycerin under the conditionsof use.

I claim:

1. A propellent powder comprising nitrocellulose 77.8%, nitroglycerin20%, "dinitrotoluene 1.2%, a stabilizer 1%, and having a 'coatingofdinitrotoluene 2 to 2. A propellent powder comprising nitrocellulose71.2%, nitroglycerin dinitrotoluene 1.2%, a high potential explosive6.6%, a stabilizer 1%, and having a coating of dinitrotoluene 2 to 10%.

3. A coated high potential double-base propellent powder comprisingnitrocellulose, nitroglycerin saturated with dinitrotoluen'e, and acoating of dinitrotoluene.

4. A coated high potential double-base propellent powder, comprisingnitrocellulose, nitroglyc- 4 erin saturated with dinitrotoluene and witha high potential explosive, and a coating of dinitrotoluene.

5. A coated high potentialdoubleebase propellent powder comprisingnitrocellulose, nitroglycerin saturated with dinitrotoluene and with ahigh potential explosive, and a coating insoluble-in nitroglycerin andwhich retards the initial burning rate of'the powder.

6. A coated high potential double-base propellent powder comprisingnitrocellulose, nitroglycerin saturated with dimethyl-diphenylurea, anda coating of dimethyldiphenylurea.

'7. A coated high potential double-base propellent powder comprisingnitrocellulose, nitroglycerin saturated with material which as a coatingfor'the powder retards its initial burning rate, and, acoatingagent ofsaid material.

-8; A coated high potential double-base propellent powder comprisingnitrocellulose, nitroglycerin, an agent-solublein nitroglycerinto-reduce its volatility, and a coating insoluble in -nitroglycerin andwhich retards the initial burning rate of the powder.

9. A coated high potential double-base propellent powder comprisingnitrocellulose, nitroglycerin, a highpotential explosive SOIllbleinmi-:troglycerin, and a coating insoluble in ni- .troglycerin and whichretards the initial burning irate "of the powder. l

.110. The process for the manufacture of coatednitroglycerinnitrocellulose powders which com- :prises saturating thenitroglycerin with a material which as 'a coating for the powder retardsits initial burning rate, and then applying a coating :agent of saidmaterial.

11. The process for the manufacture of coated'nitroglycerinenitrocellose powders which pomprises saturating thenitroglycerin with a material which as a' coating for the powder retardsits initial burning rate, saturating the nitroglycerin with a highpotential explosive, and then applying a coating of a material whichretards the initial burning rate of the powder.

12. The processfor the manufacture of coated nitroglycerinnitrocellulosepowders which coinprises saturating the nitroglycerin with a highpotential explosive, and then "applying a coating which is insoluble innitroglycerin and which retards the initial burning rate of the powder.

13. The process tor the manufacture of coatednitroglycerin-'-nitrocellulose powders which comprises adding to thenitroglycerin an agent 'for reducing its volatility, and applying "acoating which isinsoluble in nitroglycerin and which retards the initialburning rate of the powder.

14. A coated high potential double-base propellent powder, substantiallystabilized against change in ballistic characteristics during storage atelevated temperatures, said base including nitrocellulose andnitroglycerin, and a coatin'g'fo'r said base to retard the rate ofburning of the powder in the initial stages of its combustion, saidnitroglycerin containing a nitroglycerin soluble compound which rendersthe nitroglycerin non-diifusible into said coating material and ofreduced volatility, and said coating being formed of a material which isinsoluble in the modified nitroglycerin of the base.

1 5. The coated double-base propellent powder of claim 14, the materialof said coating being normally soluble in the nitroglycerin and saidnitroglycerin being substantially saturated with the material of thecoating to render the coating insoluble therein.

16. A coated propellent powder comprising nitroglycerin saturated with amaterial which when used as a coating for the powder retards its gginitial burning rate, another explosive material, 899855 and a coatingof a material which retards the in- 5 1 0906 41 itial burning rate ofthe powder. 1509393 1,716,434

GEORGE C. HALE. 2,008,889

REFERENCES CITED 10 The following references are of record in the Numberfile of this patent: 473,057

6 UNITED STATES PATENTS Name Date Williams July 3, 1906 Abelli Sept. 29,1908 Nathan Mar. 17, 1914 Bryan Sept. 23, 1924 Fidlar Q. June 11, 1929Wagner July 23, 1935 FOREIGN PATENTS Country Date Great Britain Oct. 4,1937

